Influence de facteurs environnementaux influençant la teneur en urée dans le lait de vache en Wallonie et estimation des rejets azotés

Study on environmental factors influencing the urea content of cow's milk in Wallonia and estimation of nitrogen rejection. In Wallonia (South of Belgium), the urea content of milk produced on farms is assessed by the "Comité du lait". A total of 8,295,337 pieces of data recording the urea content in milk tanks was collected on Walloon farms in 2000 and during the period 2002-2011. These data were analyzed using a linear model. The fixed effects of the agricultural area or vulnerable zone, the month, the year and the interactions between these parameters were included in the model. The levels of fat and protein content in the milk were used as covariates. The average urea content in milk was found to be 255 mg·l-1. Four percent of the observations recorded a urea content of over 350 mg·l-1 and 14% recorded a urea content of over 400 mg·l-1. The models explained 38% and 35% of the variation in milk urea for the agricultural area and the vulnerable area variables, respectively. Within these models, the variables of month, region, year and the month-year interaction were the components that provided the most information. Milk urea content was higher in the summer period – April to October – than during the winter period – November to March – (287 vs 210 mg·l-1). This observation can be explained by the change in the cows' diet. During the summer, most of the cows grazed; ingestion of grass can lead to a nitrogen surplus in the diet. In the so-called "Limoneuse" and "Sablo-limoneuse" agricultural areas, recorded urea content was lower than in "Ardenne" and "Haute-Ardenne" (223 and 220 mg vs 278 and 284 mg·l-1, respectively). This difference can be explained by a greater use of grass in the diet in Ardenne and Haute-Ardenne. In vulnerable areas, urea content was lower (236 vs 273 mg·l-1). Annual nitrogen production calculated using different prediction equations ranged from 82 to 119 kg N per cow depending on the agricultural area

The participation paradigm in audience research

As today's media simultaneously converge and diverge, fusing and hybridizing across digital services and platforms, some researchers argue that audiences are dead-long live the user! But for others, it is the complex interweaving of continuities and changes that demands attention, especially now that audiencing has become a vital mode of engaging with all dimensions of daily life. This article asks how we should research audiences in a digital networked age. I argue that, while many avenues are being actively pursued, many researchers are concentrating on the notion of participation, asking, on the one hand, what modes of participation are afforded to people by the particular media and communication infrastructures which mediate social, cultural or political spheres of life? And, on the other hand, how do people engage with, accede to, negotiate or contest this as they explore and invent new ways of connecting with each other through and around media? The features of this emerging participation paradigm of audience research are examined in this article

Prediction of nitrogen excretion from data on dairy cows fed a wide range of diets compiled in an intercontinental database: A meta-analysis

Manure nitrogen (N) from cattle contributes to nitrous oxide and ammonia emissions and nitrate leaching. Measurement of manure N outputs on dairy farms is laborious, expensive, and impractical at large scales; therefore, models are needed to predict N excreted in urine and feces. Building robust prediction models requires extensive data from animals under different management systems worldwide. Thus, the study objectives were (1) to collate an international database of N excretion in feces and urine based on individual lactating dairy cow data from different continents; (2) to determine the suitability of key variables for predicting fecal, urinary, and total manure N excretion; and (3) to develop robust and reliable N excretion prediction models based on individual data from lactating dairy cows consuming various diets. A raw data set was created based on 5,483 individual cow observations, with 5,420 fecal N excretion and 3,621 urine N excretion measurements collected from 162 in vivo experiments conducted by 22 research institutes mostly located in Europe (n = 14) and North America (n = 5). A sequential approach was taken in developing models with increasing complexity by incrementally adding variables that had a significant individual effect on fecal, urinary, or total 2manure N excretion. Nitrogen excretion was predicted by fitting linear mixed models including experiment as a random effect. Simple models requiring dry matter intake (DMI) or N intake performed better for predicting fecal N excretion than simple models using diet nutrient composition or milk performance parameters. Simple models based on N intake performed better for urinary and total manure N excretion than those based on DMI, but simple models using milk urea N (MUN) and N intake performed even better for urinary N excretion. The full model predicting fecal N excretion had similar performance to simple models based on DMI but included several independent variables (DMI, diet crude protein content, diet neutral detergent fiber content, milk protein), depending on the location, and had root mean square prediction errors as a fraction of the observed mean values of 19.1% for intercontinental, 19.8% for European, and 17.7% for North American data sets. Complex total manure N excretion models based on N intake and MUN led to prediction errors of about 13.0% to 14.0%, which were comparable to models based on N intake alone. Intercepts and slopes of variables in optimal prediction equations developed on intercontinental, European, and North American bases differed from each other, and therefore region-specific models are preferred to predict N excretion. In conclusion, region-specific models that include information on DMI or N intake and MUN are required for good prediction of fecal, urinary, and total manure N excretion. In absence of intake data, region-specific complex equations using easily and routinely measured variables to predict fecal, urinary, or total manure N excretion may be used, but these equations have lower performance than equations based on intake

Prediction of nitrogen excretion from data on dairy cows fed a wide range of diets compiled in an intercontinental database: a meta-analysis

publishedVersio

Amélioration des bilans d'excrétion d'azote dans deux exploitations laitières de la région wallonne par un suivi raisonné des rations

Improvements after precision dietary management of nitrogen rejection in two commercial dairy farms in Wallonia. Two dairy farms located in Pays de Herve and in Ardennes were followed at regular intervals in order to assess levels of nitrogen rejection. In Farm 1, the cows were divided into two groups: group HP contained high production cows and group BP contained cows with a lower production yield. Each group was offered a specific basal diet. In Farm 2, only one group of cows was assessed. The feed rations on both farms were characterized by a imbalance between the yields allowed by the energy or the nitrogen supplies and by an extremely high OEB balance of 794, 582 and 726 g, respectively, in groups HP and BP and in the Farm 2 group. Dietary changes were proposed in order to balance milk yields and to reduce the hypothesized nitrogen balance. The yield and urea content data from each milk record, along with data regarding nitrogen rejection, were statistically analyzed using a mixed model, which included an autoregressive covariance. The data from records 2, 3, 4 and 5 were then compared to the data from record 1. The advised changes implemented in the feeding management plan maintained milk yields at values similar to the yields observed in record 1 – 36.2, 24.3 and 23.0 l of 4% fat-corrected milk expressed for fixed days in milk produced by groups HP and BP and the Farm 2 group. The changes induced a significant reduction in the milk urea content (220 vs 300 mg·l-1) and a significant reduction in nitrogen rejection, whether expressed in terms of g per day per cow, g·l-1 or kg per year per cow. The cows in the Farm 2 group rejected less nitrogen in absolute terms (217.9 vs 260.1 g per day). However, it is interesting to note that the management approach in Farm 1 was more efficient in terms of nitrogen rejection since the level was on average 9 g·l-1 in comparison with 10 g·l-1 in Farm 2. In conclusion, it appears that, for either farm, whether an intensive or extensive management regime was being employed, the provision of well balanced feed rations led to a reduction in nitrogen rejection. It should, however, be noted that management advice needs to be provided on a farm by farm basis

Compensatory growth in Belgian Blue bulls previously grazed at two stocking rates: animal performance and meat characteristics

peer reviewedA comparison was made between finishing systems with Belgian Blue bulls of the double-muscle type, in order to assess the response in terms of compensatory growth when bulls were grazed at a high stocking rate. Two groups of 8 bulls (256.5 kg liveweight) were grazed on Lolium perenne and Trifolium repens pasture during an initial period of 135 days (period I). One group grazed at a stocking rate of 6/ha allowing for normal growth at pasture (NGP); the other group grazed at a stocking rate of 10/ha (low growth at pasture, LGP). Both groups were then finished indoors (period II) with a concentrate based on dried sugarbeet pulp. Eight control bulls were also finished indoors on the concentrate diet during periods I and II (CG). Bulls were slaughtered according to a similar finishing state. Liveweight gains were 1.47, 1.10 and 0.52 kg daily (P<0.001) during period I in CG, NGP and LGP groups respectively. Corresponding liveweight gains during period II were 1.22, 1.37 and 1.50 kg daily. The LGP group had lower feed conversion ratios, slaughter weights (P<0.05) and dressing proportions (P<0.01). The meat from the grazed bulls had lower cooking losses (P<0.05) and tended to have lower drip losses and higher tenderness. It also had a higher cholesterol (P<0.05) content. Large differences were observed in the fatty acid composition according to fat location (subcutaneous, intermuscular or intramuscular). The proportions of mono and polyunsaturated acids increased in the adipose tissue of those previously grazed

Effects of heat stress periods on milk production, milking frequency and rumination time of grazing dairy cows milked by a mobile automatic system in 2013

In Europe, analysis of meteorological data shows that the average temperature has increased by ~1°C over the past hundred years (IPCC, 2013). Heat stress periods are thus expected to be more frequent even in temperate areas. The use of an automatic milking system (AMS) implies the need to stimulate cows’ traffic to the robot, especially with grazing cows. Describing how heat stress influenced cows’ traffic to the robot is the aim of this study. Grazing dairy cows milked by an automatic system (AMS) experienced heat stress (HS) periods, twice during the summer 2013 in July (J) and August (A). The daily temperature humidity index (THI) during these periods were higher than 75. Each HS period was compared with a “normal period”(N), presenting the same number of cows, similar lactation number, days in milk, distance to come back to the robot and an equal access to water. The first HS period of 5 days with a mean THI of 78.4 was chosen in J, and a second that lasted for 6 days in A with a THI value of 77.3. Heat stress periods were cut off with the same duration of days with no stress (N) and mean THI &lt;70. Milk production, milkings and returns to the robot during HS were compared with N periods. Milkings and visits to AMS were significantly more numerous in HS periods in July (HS: 2.44 vs N: 2.23, 3.97 vs 3.03) but milk production dropped from 20.3 kg to 19.3 kg milk per cow and per day. In August, MY increased slightly during HS. This could be explained by less high ambient temperatures and decreased distance to walk inducing less energy expenditure. The increase in milkings and visits to the robot during HS could be linked to water availability nearby the robot and confirmed previous findings (Lessire et al., 2014)

La production de viande bovine à partir de femelles de réforme

National audienceIn the European Union, half of slaughtered adult cattle are female, including 60 % of adult cows and 40 % of heifers, mainly from dairy races. The animals are culled for multiple reasons that vary from one country to another and even from one herd to another. Fattening is therefore more difficult and haphazard than that of young bulls, due to the heterogeneity of their characteristics at the culling time, such as: age, race and format, medical and physiological statutes, and body condition score. The methods of finishing (outside or inside) and of feeding are also significant sources of variation. This article proposes to review the principal factors influencing the finishing of culled females.Dans l’Union Européenne, la moitié des gros bovins abattus sont des femelles, dont 60 % de vaches adultes et 40 % de génisses, essentiellement de races laitières. Les causes qui conduisent ces animaux à la réforme sont multiples et varient fortement d’un pays à l’autre et même d’un troupeau à l’autre. Leur engraissement est de ce fait nettement plus difficile et aléatoire que celui des jeunes taurillons, eu égard à l’hétérogénéité de leurs caractéristiques lors de la réforme. Parmi celles-ci, on peut citer : l’âge, la race et le format, l’état sanitaire, l’état physiologique, l’état corporel. Les modalités de finition (au pâturage ou à l’auge) et d’alimentation sont également des sources de variations importantes. Cet article propose de passer en revue les principaux facteurs pouvant influer sur la finition des femelles de réform

Influence du stade de maturité de la plante de maïs récoltée pour ensilage sur la composition, la digestibilité apparente, les caractéristiques de fermentation dans le rumen et les performances zootechniques chez le taurillon à l'engraissement

International audienc

Effets de la vitesse de croissance au pâturage chez des taurillons finis en stabulation : I. Performances zootechniques

peer reviewe